Starch derivatives processes for making them compositions based upon the starch derivatives and methods of making the compositions

ABSTRACT

THIS APPLICATION COVERS A PROCESS FOR PRODUCING STARCH DERIVATIVES BY OXIDIZING A STARCH THAT HAS BEEN REACTED WITH A REAGENT THAT INTRODUCES A POSITIVE ELECTRIC CHARGE INTO THE STARCH MOLECULE, UNDER CONDITIONS SUCH THAT THE REACTION PRODUCT HAS RESIDUAL UNREACTED HYDROXYL GROUPS. THE DEGREE OF SUBSTITUTION OF THE CATIONIC-TYPE CONSTITUENTS IS FROM ABOUT 0.01 TO ABOUT 0.1. ALSO COVERED ARE THE DERIVATIVES THUS PRODUCED. THE CARBOXYL GROUPS PRESENT IN THE MOLECULE, AS A RESULT OF THE OXIDATION, ARE PREFERABLY IN SUFFICIENT QUANTITY THAT THE RATIO OF THE PERCENTAGE OF CARBOXYL GROUPS BY WEIGHT, DRY BASIS, TO THE DEGREE OF SUBSTITUTION WITH THE SAID SUBSTITUENT IS AT LEAST 1 TO 1. THE APPLICATION IS ALSO ADDRESSED TO PAPER COATING COMPOSITIONS CONTAINING, AS AT LEAST A PART OF THE STARCH BINDER FOR THE COMPOSITION, A NOVEL STARCH DERIVATIVE OF THE KIND JUST DESCRIBED. ALSO COVERED ARE METHODS OF MAKING THE PAPER COATING COMPOSITIONS CONTAINING THE NOVEL STARCH DERIVATIVES.

United States Patent 3,654,263 STARCH DERIVATIVES, PROCESSES FOR MAKINGTHEM, COMPOSITIONS BASED UPON THE STARCH DERIVATIVES AND METHODS OFMAKING THE COMPOSITIONS Richard W. Cescato, Chicago, Ill., assignor toCPC International Inc. No Drawing. Filed Dec. 30, 1966, Ser. No. 608,720Int. Cl. C08b 19/06 US. Cl. 260-233.3 R 16 Claims ABSTRACT OF THEDISCLOSURE This application covers a process for producing starchderivatives by oxidizing a starch that has been reacted with a reagentthat introduces a positive electric charge into the starch molecule,under conditions such that the reaction product has residual unreactedhydroxyl groups. The degree of substitution of the cationic-typeconstituents is from about 0.01 to about 0.1. Also covered are thederivatives thus produced. The carboxyl groups present in the molecule,as a result of the oxidation, are preferably in sufiicient quantity thatthe ratio of the percentage of carboxyl groups by weight, dry basis, tothe degree of substitution with the said substituent is at least 1 to l.

The application is also addressed to paper coating compositionscontaining, as at least a part of the starch binder for the composition,a novel starch derivative of the kind just described.

Also covered are methods of making the paper coating compositionscontaining the novel starch derivatives.

This invention relates to novel starch derivatives and to methods ofmaking them. More particularly, this invention relates to novelderivatives of starch ethers and esters, and processes of making them.

This invention also relates to compositions utilizing these novel starchderivatives as binders, and to processes of making these compositions.More particularly, the invention relates to compositions that are usefulin sizing and coating paper and that contain the novel starchderivatives as binders therein.

Casein has been employed for man years in the preparation of papercoating compositions. Such compositions, based upon casein as thebinder, exhibit many desirable characteristics, among which wet rubresistance is particularly outstanding. Unfortunately, casein isrelatively expensive, is not always available, and at times exhibitsinstability. Moreover, casein requires careful handling if the papercoating compositions obtained are to be uniform and easily handled.

One object of the present invention is to provide novel starchderivatives that have new and useful properties. A related object of theinvention is to provide practical processes for producing thesederivatives.

Another object of the invention is to provide new, practical papercoating compositions and processes of making them.

A more specific object of the invention is to provide novel starchderivatives that have properties that approach those of casein for papercoating applications, which starch derivatives can be preparedeconomically, from readily available materials.

A further object of the invention is to provide novel 3,654,263 PatentedApr. 4, 1972 starch derivatives of the charater described that arefurther characterized by great stability and that can be easily preparedin a variety of forms that are convenient for use.

Still another object of the invention is to provide practical papercoating compositions that can be used to produce coatings of greater webrub resistance than has been possible in the past with coatings basedupon starch derivatives.

Another object of the invention is to provide new, practical, papercompositions based upon binders of novel starch derivatives, that willpermit higher solids paper coatings and resultant greater paper machinespeeds.

Other objects of the invention will be apparent hereinafter from thespecification and from the recitals of the appended claims.

GENERAL It has now been discovered that novel starch derivatives can beprepared on a practical basis by oxidizing an intermediate starch, thatis, a starch that has been reacted with a reagent that introduces apositive electrical charge into the molecule, under reaction conditionssuch that the intermediate starch has residual unreacted hydroxylgroups. These novel starch derivatives are extremely useful in thepreparation of compositions that are useful in the produtcion of coatedpaper products. A coating composition, in accordance with thisinvention, comprises an aqueous slurry of a material selected from thegroup consisting of fillers, pigments, and mixtures thereof, and fromabout 5% to about by weight of the material, dry basis, of a starchbinder, at least a part of said starch binder comprising an intermediatestarch that has been oxidized.

THE INITIAL STARCH The initial starch includes any amylaceous substancesuch as untreated starch, as well as starch which has been treated bychemical or other means to produce dextrinized, hydrolyzed, esterifiedor etherified derivatives of starch, so long as the product is stillessentially amylaceous in nature and still contains hydroxyl groupscapable of reacting with reagents serving to introduce a positiveelectrical charge into the molecule. The initial starch may be derivedfrom any plant sources, including com, waxy maize, sorghum, tapioca,potato, wheat, rice and sago.

For example, the initial starch may be a corn starch that has beenphosphorylated. Other suitable starch derivatives, that can be used asthe initial starch, include such derivatives, for example, ascarboxymethyl starch; carboxyethyl starch; sulfated starch; andsulfopropyl starch. In general, it is preferred that the degree ofsubstitution (D.S.) of the initial starch be no greater than 0.05, inorder to avoid swelling problems.

A phosphorylated starch, that is suitable for use as the initial starch,can be easily made in accordance with the following simple steps: drythe starch; add a concentrated solution of sodium tripolyphosphate; dry;roast for a few minutes at 275 F.300 F.; cool promptly, and wash toremove excess salt. The product obtained is a monophosphorylated starch.

THE INTERMEDIATE STARCHES AND METHODS FOR PREPARING THEM The termintermediate starch is used to identify the starch that is to beoxidized in accordance with the present invention.

The intermediate starch is prepared from the initial starch by reactionwith a reagent that introduces a positive electric charge into themolecule, under reaction conditions such that the resultant intermediatestarch has residual unreacted hydroxyl groups.

One common kind of intermediate starch comprises those starchderivatives that a commonly referred to in the art as cationic starchesor cationic starch derivatives.

Cationic starch can be prepared by reacting an initial starch, usuallyby an etherification or an esterification re action, with a reactantthat introduces a cationic group into the starch molecule. Ordinarily,such a cationic group will contain nitrogen, sulfur, or phosphorus.Cationic starch characteristically has been considered to have apositively charged molecule. Ordinarily, therefore, cationic starchwould be expected to respond to electrophoresis as a positively chargedmolecule, that is, to exhibit mobility toward the cathode at a pH ofabout 7 or 8, or perhaps, to exhibit little or no mobility. However, inthe course of the present investigations, it has been found,surprisingly, that some starch derivatives, that would ordinarily beconsidered as cationic, exhibit mobility in the direction of the anodeat pH 7-8 during electrophoresis.

For this reason, among others, reference is made in this application tostarch derivatives that are formed by reactions with reagents that reactto introduce a positive charge into the molecule, rather than to theless precise prior art terminology of cationic starch derivatives. Forconvenience, however, the term cationic-type substituent is used torefer to a substituent group that introduces a positive electricalcharge into the starch molecule, regardless of the net electrical chargeon the molecule, and regardless of the response of the starch derivativeto electrophoresis.

Examples of suitable derivative groups, that introduce a positiveelectrical charge into the initial starch molecule, are amine groups,either tertiary or quaternary, and sulfonium and phosphonium groups.

While a wide variety of such starch derivatives are available for use asintermediate starches in accordance with the present invention, it ispreferred to use the starch derivatives prepared in accordance with US.Pat. 2,876,- 217, granted Mar. 3, 195, to Eugene F. Paschall. As pointedout in that patent, starch derivatives may be prepared by reactingstarch with the reaction product of an epihalohydrin and a tertiaryamine or a tertiary amine salt. Tertiary amines suitable for theinvention may be represented by the formula Ri-III R2 3 wherein R R andR are from the group consisting of alkyl, substituted alkyl, alkene,aryl, and aralkyl, but if all three of R R and R are the same, they eachshould contain not more than 4 carbon atoms. If all three R R and R arenot the same and if R contains up to 18 carbon atoms, then R and Rshould preferably be from the group consisting of methyl and ethyl; andif R and R are joined to form a ring, then R should preferably be fromthe group consisting of methyl and ethyl.

The reaction between epihalohydrin and the amine or the amine saltresults in compounds which may be represented by the formula R4 Ni R2wherein R is 2,3-epoxypropyl if the free amine is used, and R is 3 halo,2 hydroxypropyl if a salt of the tertiary amine is employed.

The reaction between the epihalohydrin and the amine may be shown by thefollowing equations, using trimethylamine and trimethylaminehydrochloride and epichlorohydrin for illustrative purposes.

4\ (cm) re tacit 011 These products will be referred to hereinafter forthe sake of simplicity as epihalohydrin reaction products. They reactwith starch in the presence of strongly alkaline catalysts to give theaforementioned products provided the epihalohydrin reaction products arepurified to remove substantially all of the unreacted epihalohydrin andfurther provided the reaction is carried out under controlledconditions.

It is well known in the art that epihalohydrins, even in small amounts,will react with granular starch under strongly alkaline pH conditions toform cross-linked starch ethers which are nongelatinizable in boilingwater. It is impossible to control the reaction of epihalohydrin withany tertiary amine in such a manner that a substantiallyepichlorohydrin-free reaction product is formed. That is, sufiicientepihalohydrin always remains so that a nongelatinizable (cross-linked)product results when the addition product is allowed to react withstarch in the presence of strongly alkaline catalyst, However, bysubjecting the amine epichlorohydrin reaction mixture to vacuumevaporation or solvent extraction, detrimental amounts of epihalohydrincan be removed therefrom so that cross-linking does not occur to anysubstantial extent when the reagent is allowed to react with starch andan easily gelatinizable quaternary ammonium starch derivative may beprepared.

The reaction of starch and the epihalohydrin reaction product may beillustrated by the following equations wherein the reaction product oftrimethylamine and epichlorohydrin is representative:

NaOH c412- HCH2N(CH;); 01- Starch-OH As tertiary amines, it is preferredto use those possessing at least two methyl groups attached directly tothe nitrogen because of their superior reactivity to epihalohydrin toform the desired reagent. This reactivity is retained even when thethird group of tertairy amine contains as many as 18 carbon atoms, suchas is found in dimethylstearyl amine. This high reactivity is believedto result from the low order of steric hindrance imparted by the twomethyl groups, allowing for intimate contact of epihalohydrin with thefree electron pair of the tertiary amino nitrogen. By way of example,the following dimethyl tertiary amines may be mentioned as particularlysuitable for carrying out this invention: trimethyl, dimethylbenzyl,dimethyldodecyl, and dimethylstearyl amines. However, other tertiaryamines such as triethylamine, N- ethyl and N-methyl morpholine, N-ethyland N-methyl piperidine and methyl diallylamine may also be used.

Starch derivatives that are suitable as intermediate starches, for usein the present invention, may be easily prepared in accordance with thePaschall patent, by simply mixing equimolar quantities of epihalohydrinand the tertairy amine or tertiary amino salt in an aqueous system, thenallowing the reaction to proceed, preferably with agitation, until theformation of the reagent is complete. When a tertiary amine salt isemployed in the prep aration of the reagent, the pH of the aqueoussolution should be at least and preferably between 6 and 8.

The resultant addition product may be purified as desired by solventextraction or vacuum distillation, to remove unreacted epihalohydrin andamine. Specific details as to the preparation and purification of thereagent are described in the Paschall patent. The starch derivatives arethen prepared from the reagent by dissolving it in a suitable solvent,such as, for example, dioxane, isopropyl alcohol, or water, and thencombining with the initial starch. A strongly alkaline catalyst is usedto promote the reaction. Sodium sulfate or sodium carbonate may be addedto raise the gelatinization temperature of the derivatized, intermediatestarch, and in the case of sodium sulfate, to increase the reactionrate. Intermediate starches prepared under these conditions invariablyhave unsubstituted hydroxyl groups in the 6 position, and are thereforesuitable intermediate starches for use in the present invention.

Although it is preferred to work with quaternary ammonium starchderivatives, prepared as described in the Paschall patent, other typesof starch derivatives may be employed as the intermediate starch for thepresent invention.

For example, other suitable starch derivatives, for use as theintermediate starches in the present invention, include the tertiaryamino alkyl ethers that result from the reaction of starch, underalkaline conditions, with a dialkyl amino alkyl epoxide or dialkyl aminoalkyl halide or the corresponding compounds containing aryl groups inaddition to the alkyl groups.

Primary and secondary amine derivatives may also be used as well as thecorresponding starch esters. Accordingly, it is also possible to obtainsatisfactory starch derivatives, for use as the intermediate starch, byreacting, with an initial starch, materials such as, for example:: aminoalkyl anhydrides; alkyl imines; amino alkyl epoxides', amino alkylhalides; alkyl amino alkyl epoxides or halides; amino alkyl sulfates;and the corresponding compounds containing aryl groups in addition toalkyl groups.

The sulfonium and phosphonium derivatives of starch are also known inthe art. In the preparation of sulfonium derivatives of starch, forexample, starch may be reacted in an aqueous alkaline medium with abeta-halogeno alkyl sulfonium salt, vinyl sulfonium salt, or an epoxyalkyl sulfonium salt.

Additional examples of suitable intermediate starches, that containamine groups, are those that are obtained by the reaction of an initialstarch with reagents such as, for example, the following: ethyleneimine; propylene imine; isatoic anhydride; quinolinic anhydride; betadiethyl amino ethyl chloride; beta dimethyl amino isopropyl chloride;beta dimethyl amino ethyl chloride; 3-diethyl amino 1,2- epoxypropane;3-dibutyl amino 1,2-epoxypropane; 2- bromo-S-diethyl amino pentanehydrobromide; N-(2,3- epoxypropyl) piperidine; N,N-(2,3-epoxypropyl)methyl aniline. The various halides (e.g., chloro-, bromo, etc.) can beused interchangeably. In the above reagents, where the free amines havebeen indicated (e.g., beta diethyl amino ethyl chloride), one can alsouse the hydrochloride or other salts of these reagents (e.g., betadiethyl amino ethyl chloride hydrochloride). In fact, it is ordinarilypreferred to use the salts since these tend to be less toxic and moreeasily handled. The hydrochloride moiety takes no part in the reactionwith the starch. It will be seen that beside the alkyl, aryl and aralkyltypes, the reagents may also include those containing cyclic groups.Therefore, when reference is made herein to the alkyl, aryl or aralkylgroups, it will be understood that these cyclic reagents are equivalentsof those types. It should also be mentioned that the starch-amineproducts may be subsequently treated by known methods, so as to resultin the quaternary ammonium salt, or such a quaternary ammonium salt maybe made directly from raw starch by treating it with the reactionproduct of an epihalohydrin and a tertiary amine or tertiary amine salt.In either case the resulting starch derivative is suitable for use asthe intermediate starch of this invention.

The intermediate starches may be characterized by a variety of differentresponses to electrophoresis and to other tests that are intended toidentify net molecular electrical charge, degree of ionization, and thelike. Thus, for example, a monophosphorylated starch may be used as theinitial starch, and will be characterized by a response toelectrophoresis that is typical of what the prior art refers to as ananionic material. Following reaction of this initial starch with areagent that introduces a positive electrical charge into the molecule,it may nevertheless be found that the resultant intermediate starch hasa response to electrophoresis that is characteristic of an anionicmaterial.

The present invention is particularly concerned with those oxidizedintermediate starches that are useful for paper coating and sizing.Those intermediate starches, that are considered suitable for theseapplications, are those having a degree of substitution of cationic-typesubstituents of from about 0.01 to about 0.1; and for use in claycoatings for paper, for high wet rub resistance and other desirableproperties, it is preferred that the degree of substitution be fromabout 0.01 up to about 0.07 in both cases (as measured subsequent tooxidation).

THE OXIDATION STEP The oxidation process that is employed, for oxidationof the intermediate starch, is the type of oxidation process that isknown in the art for the oxidation of starch. The important and criticalfeature of the present invention, however, is that this oxidation stepmust be applied to an intermediate starch, as defined above, in order toachieve the results of the present invention. To say the same thinganother way, the same kinds of starch derivatives and the sameproperties are not obtained if an oxidized starch is reacted, afteroxidation, with a reactant that introduces a positive electrical chargeinto the molecule. It is essential that the oxidation step be applied tothe intermediate starch.

To accomplish oxidation, the intermediate starch is placed in an aqueousmedium and is subjected to the action of a starch oxidizing agent, suchas, for example, sodium hypochlorite, at a temperature in the range fromabout fl0 F. to about 120 F., and preferably, at a temperature 1n therange of from about F. to about F. Ordinarily a period of two or threehours suffices for completion of the oxidation reaction. Other exemplaryoxidizing materials that can be employed, in place of sodiumhypochlorite, include sodium bromite, sodium chlorite, calciumhypochlorite, and the like.

THE OXIDIZED PRODUCTS The oxidized products of the present inventiongenerally have a white appearance. They may be either granular orpregelled. That is, they may be similar in appearance to either pearlstarch or powdered starch, depending upon the physical characteristicsdesired in the end product. They can be produced in any desired physicalform that is processed by the starch industry today.

Upon chemical analysis, the degree of substitution of the cationic-typesubstituent can be measured by conventional techniques. For example,when the intermediate starch used is a quaternary amine derivative,classical analytical techniques to measure the presence of nitrogenprovide an accurate measure of the degree of substitution withcationic-type substituents. Ordinarily, the degree of substitution asmeasured subsequent to oxidation is found to be somewhat (slightly)lower than the degree of substitution as measured prior to oxidation.

The oxidation step normally introduces carboxyl groups and carbonylgroups into the starch molecule. For analytical convenience, thecarboxyl groups have been measured on a weight basis and are so referredto herein. Conventional analytical techniques are employed to determinethe amount of carboxyl present in the starch molecule.

As is customary, the figures included herein describing starchderivatives are statistical averages representing measurements made on asample containing a representative and large number of molecules, andthe measurements would not be expected to hold true of any individualmolecule within the sample mass, necessarily.

The following examples illustrate several preferred embodiments ofoxidized products made in accordance with the present invetnion. Allparts and percentages referred to hereafter are by weight, dry basis,unless otherwise expressly so stated.

For clarity, the material obtained by oxidation of the intermediatestarch is and has been referred to as the oxidized product. As will beseen, the oxidized product may have a response to electrophoresis orstaining tests that is characteristic of what the prior art would referto as either cationic, anionic, or nonionic starch derivatives.

Example 1 Four different batches of oxidized products, hereafterdesignated as batches 1A, 1B, 1C, and 1D, were prepared by oxidizingintermediate starches, as will now be described in detail.

The intermediate starch was the same for the preparation of the twostarch batches 1A and 1B, and was prepared in the following way.

0.2 mole (49 g. of aqueous solution) of trimethylamine and 0.2 mole(18.5 g.) of epichlorohydrin were mixed with 50 ml. of water and themixture agitated for three hours at room temperature. The resultingsolution was concentrated to a thick syrup by vacuum distillation at C.and 10-30 mm. pressure, while collecting the volatiles in a dry icetrap.

A slurry containing one mole (162 g. dry basis) of unmodified cornstarch, 250 ml. of water, 0.17 mole (10 g.) of NaCl and 0.07 mole (2.8g.) of NaOH was then added to the flask containing the syrup and themixture was stirred for 17 hours at C. The reaction mixture then wasneutralized to pH 7 with HCl, the resulting starch ether was filtered.The filter cake was washed with water.

The intermediate starches for the preparation of oxidized products 1Cand 1D were prepared in a generally similar manner, but with a lesseramount of the amineepichlorohydrin reactant.

The analyses of these four intermediate starches are summarized below inTable 1.

TABLE 1,ANALYSES OF THE INT ERMEDIATE STARCHES These intermediatestarches were then subjected to oxidation by slurrying the individualintermediate starches, respectively, in water, heating, then addingsodium hypochlorite while gently agitating the slurry, and permittingthe oxidation reaction to go forward for about three hours. At the endof the reaction period, a suflicient quantity of dilute sulfuric acidwas added to each slurry to adjust to a pH of about 6.0, then sodiumbisulfite was added to obtain a negative reaction to orthotolidene.

The oxidation reaction conditions are described below in Table 2.

TABLE 2.-SUMMARY OF OXIDATION REACTION CONDITIONS 1A 1B 1C 1D Slurry, Be20 20 20 20 Starch solids (D.B 35. 5 35.5 35. 5 35.5 Slurry pH 7. 0 7. 05. 5 5. 6 Slurry temp., F. 104 105 105 105 Sodium hypoehlorite,expressed as percent chlorine on starch 4. 0 5. 0 4. 0 4. 0 pH afterhypo addition 11.0 10. 9 10. 0 10. 1 1:3 I-IzS04 added to pH 6. 7 6.16.2 6. 1 Total reaction time (hours) 3 3 3 3 B.S.S. (sodium bisulfite)added to Negative o-tolidene The oxidized products that were recoveredfrom these oxidation reactions had the characteristics that aresummarized below in Table 3.

TABLE 3.ANALYSES OF OXIDIZED PRODUCTS 1A 1B 1C 1D Moisture, percent 12.1 7. 1 11. 2 9. 1 pH 7. 7 7. 2 7. 7 7. 3 Scott viscosity:

100 gram, secs 74 46 66 gram, secs 59 Degree of cationic-type sub 210.019 Carboxyl, percent 0. 10 0. 30 0. 28 0. 26 Solubles (D.B.),percent... 1. 61 4. 00 1. 57 2. 26 Ash, percent 1. l1 1. 97 1. l6 1. 17Methylene blue stain, percent positive. 10 35 90 90 SF green stain 1Negative.

The technique of applying stains to granular starches, for the purposeof obtaining a reaction that indicates that the starch is either anionicor cationic, is well known. -A positive reaction to a methylene bluestain indicates that the substrate material is anionic. A positivereaction to SF green stain indicates that the substrate material iscationic. These tests are roughly equivalent to electrophoresis testing,but generally lack the precision of indication of net molecular chargethat response to electrophoretic testing may permit.

As Table 3 indicates, all four of the oxidized products, that wereprepared in this example, were anionic in character as determined bymethylene blue dye staining techniques. The four oxidized products werepasted and subjected to electrophoresis at pH 8. All were characterizedby anionic mobility, thus tending to confirm the results obtained by dyestaining. A pH of 8 was selected since clay coatings for paper arefrequently applied at a pH of from about 7 to about 8, and a pH of about8 is frequently used in commercial operations.

These four oxidized products were then evaluated as binders in claypaper coatings, in the following manner.

CLAY COATING PROCEDURE A clay slip was prepared, at 76% solids, by thefollowing procedure. 0.3% of tetrasodium pyrophosphate, based on clay,and 0.8% of a 10% aqueous solution of sodium hydroxide, based on thetotal slip, were added to the necessary amount of water. Kaolin KCS claywas then added, and the entire slip was agitated for 30 minutes.

The four oxidized products were then separated into several separatebatches, as will appear from the tables below, to permit severalexperimental evaluations of the oxidized materials in paper coatings.Some of the oxidized products were lcooked at 17.5% solids, others at27.5% solids, on a. steam bath at 200 F.-205 F. for 30 minutes, withagitation during the first five minutes or so. The resultant pastes werethen cooled to about 150 F., and brought back to weight with addedwater.

Different batches of coating colors were prepared at 60% solids-18%adhesive and at 50% solids-18% adhesive, respectively. The materialsused in making the coating colors were added in the following order:

(1) Clay slip at 76% solids.

(2) Starch paste at either 17.5% solids or at 27.5% solids, dependingupon the coating solids percentage desired.

(3) The insolubilizing agent, if employed, which would be either glyoxalat 40% solids, or Parez 613 (a commercially availablemelamine-formaldehyde resin) at 80% solids.

l viscosity at 20 r.p.m., on the ascending side of the viscosity curve,then dividing by the viscosity at 20 r.p.m. on the descending side ofthe coating curve.

Each coating was applied to paper in the following 5 manner. One set ofcoated paper was made with Mayer rod drawdowns, with each coating inthis set being applied at 60% solids. The paper was first air-dried fortwo hours, and then dried in a forced air oven at various temperatures,as indicated in the following tables, for short periods of time.

A second set of coated paper was made by applying coatings at 50% solidson coating base stock, with the trailing blade attachment of a papercoater. The coated paper was calendered by three nip passes at 600 lbs.per linear inch, with heat. The paper was then conditioned for 24 hoursin a constant temperature and humidity room at 50% relative humidity andat 72 F., prior to evaluation.

The several observations are recorded in the following tables:

TABLE 4.-VISCOSITY OF CLAY COATINGS, 50% SOLIDS, 18% ADHESIVE WITHGLYOXAL Batch 1A 1B 1C 1D Percent glyoxal 0 1 3 5 7 10 5 10 5 10 5 10Brookfield viscosity, cps.: At 11 F., r.p.m.:

7,000 6,500 8, 500 20,000 22,500 33, 000 2, 500 4, 500 20,000 42, 50017,000 29, 500 4,200 3,900 4, 800 11, 000 11,400 17, 500 1, 600 2, 90011, 500 24, 500 10, 000 16,000 2, 200 1, 900 2, 300 5, 000 4, 900 6, 800930 1, 900 5,500 10, 800 4,500 7, 200 1, 300 1, 100 1, 350 2, 600 2, 5003, 500 600 950 3, 150 5, 700 2, 400 4,000 2, 000 1, 700 2, 100 4, 300 4,100 5, 800 850 1, 500 4, 800 9, 700 3, 600 6, 500 3, 500 2, 900 3, 6008, 800 8, 500 12,500 1, 500 2, 700 8,800 19, 400 6, 400 12, 500 5, 5005, 000 6, 000 15, 500 15,000 23, 000 2, 100 4, 300 14, 000 33,500 10,500 21,500 1,600 1, 200 1, 150 2, 350 2, 400 3,200 600 800 2, 750 4, 5501, 850 2, 950 4, 000 3, 200 3,000 8, 000 6, 500 11,000 1,500 1,200 8,20015, 000 5,000 8,600 pH 8.6 7.7 7.4 7.3 7.1 7.0 7.4 7.2 7.5 7.4 7.5 7.4Thixotropic value 1. 2O 1. 34 1. 33 1. 1. 34 1. 1- 07 1.07 1. 31 1.26 1. 56 1. 28 Pseudoplastio index 4. 23 4. 55 4. 5. 95 6- 00 6. 58 3-514. 53 4. 45 5. 87 4. 40 5. 38

Paper Physical Properties Dow wet rub passes:

Initi 2 2 5 15 15 25+ 15 30+ 15 25 15 25 2 2 5 15 15 25+ 15 30+ 15 25 1525 2 2 5 16 15 25+ 15 30+ 15 25 15 25 13 12 12 13 13 14 13 14 13 13 1313 Brightness 75 75 75 75 75. 5 75. 5 75. 5 75. 5 75. 5 75. 5 75 75Opacity 89. 5 89.0 88. 5 88.5 88. 5 89 88 88.5 88. 5 88 88. 5 88 Gloss21 19 18 22 18 20 22 20 20 21 21 21 Basis weight (24 x 38 Lbs/ream 51. 651. 6 51. 2 50. 5 51. 1 51. 1 49. 7 49. 8 49. 6 49. 7 60. 3 49. 8 Lbs.coating/ream. 4.1 4. 2 B. 7 3.0 3.6 3.6 2. 2 2. 3 2. 1 2. 2 2. 8 2. 3

After mixing the materials for a particular coating composition, thecomposition was thoroughly agitated for about 15 minutes. The pH wasthen determined, and each coating was placed in an air-tight containerand held for two hours at about 110 F. in a constant temperature waterbath.

Several characteristics of each coating composition were then observed.Thus, an initial viscosity determination was made on each coatingcomposition after it had been held for two hours at 110 F., using aBrookfield Viscometer, Model RVF. Readings were taken at 10 r.p.m., 20r.p.m., r.p.m., and 100 r.p.m. The viscometer speed was then slowed andreadings were taken during deceleration at 50 r.p.m., 20 r.p.m., and 10r.p.m. Viscosity readings were also made on each coating after 24 hoursat 110 F. at 100 r.p.m. and then at 20 r.p.m.

For convenience in evaluation of the characteristics of the coatings,reference is made hereafter to the Pseudoplastic Index. This indexnumber was obtained by measuring the Brookfeld viscosity at 10 r.p.m. onthe descending side of the viscosity curve, and dividing by the apparentviscosity at 100 r.p.m.

The characteristics of the coatings are also indicated by a value thatis hereafter referred to as the Thixotropic value. This value wasdetermined by reading the apparent 50 TABLE 6,-VISCOSITIES OF CLAYCOATINGS, 50% SOLIDS,

18% ADHESIVE WITH PAREZ 613 (MELAMINE-FORMALDE- HYDE) Starch derivativebatch Oxidized product 1A Percent Parez 613 0 3 5 7 10 Brookfieldviscosity, Gps.,:

At 110 F., r.p.m.:

pH Thixotropic value. Pseudoplastie inde Paper Physical Properties Dowwet rub passes:

Initial 75 Lbs./coating 4. 1 3.0 3.2 3.2 3.5

Percent Parcz 613 Broolorfield viscosity, cps. at 110 F., r.p.m.: 1

Pseudoplastic index Paper Physical Properties (Mayer rod drawdowns) Dowwet rub passes:

Air-dried 2 2 3 minutes at 200 F 2 2 2 minutes at 300 F 2 TABLE7.VISCOSITIES OF STARCH PRODUCTS EMPLOYED IN COATINGS Oxidized productStarch batch 1A 1B 1C 1D Percent solids 17.5 27.5 17.5 17. 5 17. 5

Brookfield viscosity, rpm,

cps. at:

200 12 50 13 17 16 150 F 32 130 18 38 33 110 F 45 180 30 73 59 77 (2 107450 53 180 128 77 F. (24 hours) 118 660 53 254 150 pH (paste) 7. 7 7. 86. 7 7. 0 7. 0

These data demonstrate that paper coatings made in accordance with thepresent invention have several advantageous characteristics that makethem particularly desirable for practical use. For example, the coatingcompositions are characterized by flow properties that permit thecompositions to be applied readily by the highly mechanized coatingprocess techniques that are currently in use. The compositions have theability to retain water sufiiciently so that upon application to paper,the loss of water into the paper web is at a level that does not have adeleterious effect upon the coating. Moreover, compositions made inaccordance with the invention have excellent stability, as demonstratedby the fact that substantial changes in viscosity do not occur.

In addition, the data demonstrate the inherent capability of theoxidized products of the present invention to function for their desiredpurpose, which means that the delicate electrostatic balance of thecoating compositions has not been disturbed. The oxidized products arelight in color and therefore are compatible with compositions of anydesired pigmentation. Also, coating compositions made in accordance withthe present invention have been 12 well to give desired smoothness andgloss without undesirable adherence of the coated paper to the surfaceof the calender rolls.

EXAMPLE 2 Five different batches of oxidized products, hereafterdesignated as batches 2A, 2B, 2C, and 2E, respectively, were prepared byoxidizing intermediate starches, as will now be described in detail.

The intermediate starch was the same for the preparation of the threebatches 2A, 2B and 2C. This intermediate starch was similar to that usedfor batch 1C, as will appear from the analyses below, and it wasprepared substantially in the manner described in Example 1.

The intermediate starches that were used for the preparation of batches2D and 2E respectively were commercially available materials having thecharacteristics described below.

TABLE 8.ANALYSES OF THE INTERMEDIATE STARCHES These intermediatestarches were subjected to oxidation by the same technique as wasemployed in Example 1. The oxidation reaction conditions are describedbelow in Table 9.

TABLE 9.-OXIDATION REACTIONS WITH SODIUM HYPO- OHLORITE Parent material2A 2B 2C 2D 2E Sodium hypochlorite, expressed as percent Chlorine onstarch... 3 4 5 4 4 Slurry Data Slurry, B 20 20 20 20 20 Starch solids(D.B.) 35. 5 35. 5 35. 5 35. 5 35. 5 pH 7.1 7.1 7.1 5.7 5.8 Temperature,F 115 115 115 115 115 Reaction Data pH after hypo addition 10. 4 10. 410. 4 9.8 10. 9 Reaction time (hours)- 4 4 4 3 3 1:3 H2804 to pH 6.6 6.66.6 6.6 6.5

Bisodium sulfite (B.S.S Negative o-tolidone TABLE 10.-ANALYSES OFOXIDIZED PRODUCTS Product 2A 2B 2C 2D 2E Moisture, percent 12.6 10.610.8 9.6-

H 7.6--. Scott viscosity" 100 g./4 Carboxyl, percent 0.51.. Degree ofcationic-type substitution 0.014- Methylene blue Pos SF green Neg NegNeg Slightly pos-. Neg

found to be receptive to printing in'ks of various types with adesirable balance between ink penetration and resistance to inkpenetration. Moreover, coated papers These five oxidized products wereevaluated as binders in clay paper coatings, in essentially the samemanner as described in Example 1. Similar observations were then made inaccordance with the present invention calender made, as recorded below.

TABLE 11.CLAY COATINGS 50% SOLIDS, 18% ADHESIVEOXIDIZED STARCHESOxidized product 2A-1 2A-2 2B-1 2B-2 2C1 20-2 2D-1 2D-2 2E-1 2E-2Percent Clz on starch 3 3 4 4 5 5 4 4 4 4 Percent glyoxal 0 5 0 5 0 5 05 Brookfield viscosity, cps.: At 110 F., r.p.m.:

5,750 980 1, 360 700 1, 060 6, 500 14, 000 3, 500 5, 800 19, 800 2,4503, 750 1, 700 2, 750 18, 700 40,000 9, 000 18, 000 pH 7. 9 8.8 8.0 8. 77. 9 8. 3 7. 4 8. 3 7.6 Thixotropie value 1. 26 1. 13 1. 24 1. 22 1.23 1. 29 1.14 1.18 1.16 Pseudoplastic index 4. 54 6- 05 3- 89 4- 30 3.33 3. 59 4. 73 4. 50 4. 17 5. 18

Coated Paper Physical Properties Dow wet rub (passes) dried at:

220 F., 1 7 1 5 1 3 1 5 1 5 220 F., 3 mm. 1 1 5 1 3 1 5 1 5 220 F., 5 m11 10 1 7 1 5 2 7 2 5 Air-dried 1 5 1 3 1 2 1 3 1 3 Dennison Wax pick at16 16 14 14 13 14 14 13 11 12 Basis weight x 38-500): LbsJream 55- 756-3 56-8 56. 4 56. 3 56. 5 56. 5 58.1 56. 0 57. 3 Coating wt., lbs 7- 78-3 8.8 8. 4 8.3 8.6 8.5 10.1 3. 0 9. 3

All of these oxidized products are useful as binders for clay coatings,as the above data demonstrates.

CONCLUSION Similar demonstrations of the invention have shown that thestep of oxidizing intermediate starches is generally useful in producingnovel, valuable products from starch derivatives that have had apositive electrical charge introduced into the molecule duringderivatization.

For example, the process of the present invention produces valuableproducts, for use in clay coatings, sizings, and in other applications,from starches that are substituted with amine, sulfoniurn, andphosphonium groups. Some exemplary starch derivatives, that oxidize toyield valuable products, are the starch ethers derived by reacting cornstarch under alkaline conditions, with agitation, with:

(a) b-diethyl amino ethyl chloride hydrochloride (b) b-dimethyl aminoethyl chloride hydrochloride (c) b-diethyl amino ethyl chloride (d)b-dimethyl amino isopropyl chloride hydrochloride (e) 3-dibutyl amino1,2 epoxypropane (f) 2-bromo-5-diethyl amino pentane hydrobromide (g)N-('2,3-epoxypropyl) piperidine (h) N,N-(2,3 epoxypropyl) methyl aniline(i) 2-chloroethyl-methyl-ethyl sulfonium iodide (j) benzyl methyl2-chloroethyl sulfonium iodide (k) 2-ch10roethyl tributyl phosphoniumchloride Other exemplary starch derivatives, that are similarlyvaluable, are made by reacting other starches, such as, for example,potato, sago, and tapioca starches, with these and similar reactants.

The intermediate starch that is used in the practice of this inventionmay be one that does not have a net posi tive electrical charge. Forexample, a phosphorylated starch may be reacted with a reagent thatintroduces a positive electrical charge into the molecule, while leavingthe molecule nevertheless with a response to electrophoresis that ischaracteristic of an anionic material. Upon oxidation, products areobtained that are highly useful in the wet sizing of paper and asbinders for paper coatings.

In order to achieve superior characteristics in a clay coating on paper,certain chemical characteristics of the oxidized products of thisinvention can be adjusted. In the following remarks, it should beunderstood that the term cationic D.S. refers to the degree ofsubstitution by a substituent that introduces a positive electricalcharge into the molecule (whether or not the molecule itself carries anet positive charge). The term percent carboxyl refers to the weight ofthe group COOH, present in the oxidized product, as compared to theWeight of the oxidized product, expressed on a percentage basis.

Generally, as to wet rub resistance and a good wax pick test, superiorresults are obtained with oxidized products that have: higher cationicD.S., that is, above the lower limit figure of about 0.01 and toward theupper limit figure of about 0.1; lower ratios of percent carboxyl/cationic D.S. quaternary amine derivatives as compared to other aminederivatives; and a response to electrophoresis at a pH of from about 7to about 8, or at pH 8, that is characteristic of a cationic material,as compared to oxidized products that exhibit responses that arecharacteristic of either nonionic or anionic materials, where the termscationic, anionic, and nonionic, are used to denote net molecularcharge, or mobility, as determined by electrophoresis of a pastedproduct.

Oxidized products made in accordance with the present invention haveproperties, with respect to paper coating and sizing, that differ inkind from those produced by first oxidizing a starch, then derivatizingwith a substituent that introduces a positive charge into the molecule.For example, as to wet rub resistance, under comparable conditions ofobservation, the difference in favor of the oxidized products of thepresent invention is a factor of at least two times.

While the invention has been described in connection with specificembodiments thereof, it will be understood that it is capable of furthermodifications, and this application is intended to cover any variations,uses or adaptations of the invention following, in general, theprinciples of the invention and including such departures from thepresent disclosure as come within known or customary practice in the artto which the invention pertains and as may be applied to the essentialfeatures hereinbefore set forth, and as fall within the scope of theinvention and the limits of the appended claims.

I claim:

1. A process for producing novel starch derivatives comprisingsubjecting a starch material, that has been reacted with a reagent thatintroduces a positive electric charge into the starch molecule, underconditions such that said starch material, after reaction with saidreagent, has a degree of substitution with a cationic-type substituentof from about 0.01 to about 0.1, and has residual unreacted hydroxylgroups, to oxidation by a starch oxidizing agent of the sodiumhypochlorite type in a basic pH environment, simultaneously to thin thestarch material and to introduce carboxyl groups into the starchmolecule.

2. A process for producing novel starch derivatives comprising:subjecting a starch derivative, that has a degree of substitution ofcationic-type substituents of from about 0.01 to about 0.1 to oxidationby a starch oxidizing agent of the sodium hypochlorite type, in a basicpH environment, simultaneously to thin the derivative and to introducecarbonyl and carboxyl groups into the starch molecule, and recovering anoxidized product having a degree of substitution of carboxyl groups atleast equal to that of the cationic-type substituent.

3. A process in accordance with claim 2 wherein the starch derivative isselected from the group consisting of starch ethers and starch esterscontaining substituents selected from the group consisting of primary,secondary, tertiary and quaternary amine groups, sulfonium groups, andphosphonium groups.

4. A process in accordance with claim 3 wherein the oxidation is carriedto the point where the net charge on the molecule is positive asdetermined by electrophoresis at a pH of from about 7 to about 8.

5. A process in accordance with claim 3 wherein the oxidation is carriedto the point where the net charge on the molecule is negative asdetermined by electrophoresis at a pH of from about 7 to about 8.

6. A process in accordance with claim 3 wherein the oxidation is carriedto the point where the net charge on the molecule is such that there issubstantially no response to electrophoresis at a pH of from about 7 toabout 8.

7. Novel starch derivatives produced according to the process of claim4.

8. Novel starch derivatives produced according to the process of claim5.

9. Novel starch derivatives produced according to the process of claim6.

10. A process for preparing novel starch derivatives comprising;reaction together:

(a) the reaction product of an epihalohydrin and a compound selectedfrom the group consisting of tertiary amines and tertiary amine salts,from which reaction product substantially all of the unreactedepihalohydrin has been removed, the tertiary amine being represented bythe formula wherein R R and R are radicals containing not more than 18carbon atoms from the group consisting of alkyl, substituted alkyl,alkene, cyclic formed by joining two Rs as previously defined, phenyland monocyclic aralkyl and when all three Rs are the same each is analkyl group containing not more than 3 carbon atoms, and when all threeRs are not the same and any R contains more than 3 carbon atoms, thenthe other two Rs are each an alkyl group not larger than ethyl, and whentwo Rs are joined to form a ring, then the third R is an alkyl group notlarger than ethyl; and

(b) a starch material, in contact with a strongly alkaline catalyst, toform a starch derivative having a degree of substitution effected bysaid reaction of up to about 0.1; mixing the starch derivative into anaqueous medium; adding a starch oxidizing agent of the sodiumhypochlorite type to the resultant slurry, thereby to oxidize the starchderivative in a basic pH environment, to introduce carbonyl and carboxylgroups into the molecule and to reduce the molecular size, andrecovering the oxidized product.

11. A novel composition of matter comprising a starch derivative thathas a degree of substitution with a cationic-type substituent of fromabout 0.01 to about 0.1, that introduces a positive electric charge inthe molecule, and that has been subjected to an oxidation step with astarch oxidizing agent of the sodium hypochlorite type in a basic pHenvironment, subsequent to derivatization with said substituent, toelfect carboxyl formation and to reduce molecular size, whereby thederivatized, oxidized starch molecule contains both positively andnegatively charged groups.

12. A composition of matter in accordance with claim 11 wherein thecarboxyl groups are present in the molecule, as a result of theoxidation, in sufficient quantity that the percentage of carboxyl groupsby weight, dry basis, is at least 0.01%.

13. A new starch ether that has a degree of substitution with aquaternary ammonium nitrogen substituent of from about 0.01 to about0.1, said quaternary derivative being the product prepared byetherifying starch in contact with a strongly alkaline catalyst, withthe reaction product of epihalohydrin and a compound from the groupconsisting of tertiary amines and tertiary amine salts; said reactionproduct being substantially free of unreacted epihalohydrin; thetertiary amine being represented by the formula wherein R R and R areradicals containing not more than 18 carbon atoms from the groupconsisting of alkyl, substituted alkyl, alkene, cyclic formed by joiningtwo Rs as previously defined, phenyl and monocyclic aralkyl and when allthree Rs are not the same and any R contains more than 3 carbon atoms,then the other two Rs are each an alkyl group not larger than ethyl, andwhen two Rs are joined to form a ring, then the third R is an alkylgroup not larger than ethyl; then oxidizing the resultant starchderivative with an oxidizing agent of the hypo chlorite type, in a basicpH environment, to introduce carbonyl and carboxyl groups into themolecule and to reduce molecular size.

14. A new starch ether in accordance with claim 13 wherein the carboxylgroups are present in the molecule in an amount of at least 0.01% byweight, dry basis.

15. A process for producing novel starch derivatives comprising reactinga starch derivative containing a substituent that introduces a positiveelectric charge in the molecule, wherein the said substituent is presentat a degree of substitution of from about 0.01 to about 0.1, with astarch oxidizing agent of the hypochlorite type, in a basic pHenvironment, to efiect carbonyl formation, carboxyl formation, andthinning, in the starch molecule.

16. A process for preparing novel starch derivatives comprising:reacting together:

(a) a monophosphorylated starch, and

(b) the reaction product of an epihalohydrin and a compound selectedfrom the group consisting of tetriary amines and tertiary amine salts,from which reaction product substantially all of the unreactedepihalohydrin has been removed, the tertiary amine being represented bythe formula Rr-III-Rg s wherein R R and R are radicals containing notmore than 18 carbon atoms from the group consisting of alkyl,substituted alkyl, alkene, cyclic formed by joining two Rs as previouslydefined, phenyl and monocyclic aralkyl and when all three Rs are thesame each is an alkyl group containing not more than 3 carbon atoms, andwhen all three Rs are not the same and any R contains more than 3 carbonatoms, then the other two Rs are each an alkyl group not larger thanethyl, and when two Rs 1 7 are joined to form a ring then the third R isan alkyl group not larger than ethyl;

in contact with a strongly alkaline catalyst, to form a derivativehaving a degree of substitution of up to about 0.1 of the aminesubstituent; oxidizing the resultant derivative in an aqueous mediumwith a starch oxidizing agent of the hypochlorite type, in a basic pHenvironment, to introduce carbonyl and carboxyl groups into the starchmolecule, and to reduce molecular size, and recovering the oxidizedproduct.

References Cited UNITED STATES PATENTS 2,989,520 6/ 1961 Rutenberg260233.3 15 3,077,469 2/ 1963 Aszalos 260233.3 3,087,852 4/ 1963Hofreiter 162-175 18 3,067,088 12/1962 Hofreitcr 162l75 2,876,217 3/1959Paschall 260233.3

FOREIGN PATENTS 6616168 5/1967 Netherlands 260233.3 6703738 9/1967Netherlands 260233.3

FOREIGN PATENTS Whistler et al., Starch: Chemistry and Technology, vol.1 (1965), TP 415 W4, pp. 469-478.

DONALD E. CZAJA, Primary Examiner M. I. MARQUIS, Assistant Examiner U.S.Cl. X.R.

106214 R; 117156 R; 165 R; 260233.3 A, 233.5 R

